Signal flag



FIG. 1 is a front elevational view of a signal flag showing my new ornamental design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a left side elevational view thereof;

FIG. 4 is a rear elevational view thereof;

FIG. 5 is a right side elevational view thereof; and,

FIG. 6 is a bottom plan view of the flag of FIG. 6. 

The ornamental design for a signal flag, as shown and described. 